Type number of old Ge power transistor

That was likely the 2N301, a Ge PNP unit in TO-3. It did have pretty good Hfe for a power transistor of that vintage - minimum of 50. I used a couple to build my first solid state guitar amp in the 1960s. See the datasheet at

Cheers,

Dave M

I remember having to replace a pair of 2N1536 AF output in a 16mm film projector in the 1970s (reminded of film projector by your tale in another post).

Recently I used a junk box AD149 to switch a house doorbell at 2V and was reminded of how low Vce(sat) in Ge is. Was losing 30mV at 500mA and my junkbox MOSFETs capable of doing that would have needed much higher gate voltages than 2V! What was shocking is how leaky those Ge power devices were. 40-50uA even at room temp.

piglet

The ~halved bandgap means it's basically the same as silicon operating at double the absolute temperature. Same reason for the very low max operating temp (75 C?), and driftiness in many uses.

Drift could be avoided with proper temp-compensating designs, but in the

Tim

My first transistorized audio power amplifier used a Delco DS501 "door-knob" device, class-A, ~5W... ~1957-58

I remember the date range because I began dating my wife-to-be on October 7, 1957, and her father, a machine shop operator, machined me a heat-sink. ;-) ...Jim Thompson

I don't think so.

Ic(max) of 3A is too low, and I'm sure the type number had four digits.

My first job interview, I said that I preferred tubes for my personal stuff, because transistors were expensive and easy to blow up. The guy sniffed and said "that won't do" and dismissed me. The next guy laughed and hired me, and I designed $200 million worth of stuff for him.

Really, germanium transistors weren't very rugged or reliable. The first good transistors were the Fairchild silicon planars.

Early plastic-packaged digital ICs - RTL, DTL, early TTL - were pretty bad, too. Hardly anything fails nowadays.

The Delco DS501 was used successfully in the automotive environment. Did you miss the door-knob packaging part?

Early plastic (phenolic) package chemistry ate the Aluminum metalization. ...Jim Thompson

I'm pretty sure Ic(max) wasn't as high as the 10A rating for those transistors.

I remember those 16mm projectors too. Had to repair a few for a government publicity agency. No TV here yet in the 70s in this remote corner of India.

Yes, the low Vce(sat) was one of the reasons I was reluctant to switch to Si in my projects - for my own use or custom-designed for others, especially for low-voltage applications. Another factor was the significantly more linear gain compared to Si transistors.

Oh, and the lenses of those 16mm projectors make really neat hand-held microscopes. No distortion or chromatic aberration, and more powerful than magnifying glasses. I saved a couple from discarded projectors and I still use them all the time. The downside is that you have to hold them quite close to the object.

I'm 99% sure there's a 5 and no 7.

d Hfe.

as others have said, look at the audio output stages of of car radios of th e 60's era. They were class A transformer coupled to the speaker. A can't remember now if the rest of the radio was typically solid state or low pla te voltage tubes. I seem to recall the audio output transistor was the only solid state device but the tubes operated a low plate voltage. Dos that m ake sense? m

the 60's era. They were class A transformer coupled to the speaker. A can 't remember now if the rest of the radio was typically solid state or low p late voltage tubes. I seem to recall the audio output transistor was the on ly solid state device but the tubes operated a low plate voltage. Dos that make sense?

I've seen a 12v anode valve car radio with class A germanium output proudly labelled on the front 'transistor'

NT

Now they hook up a tube's filament and call it a "vacuum tube" and sell it for four figures.

It does. Conditions here in those days were too primitive for anyone to have a car radio, but I read about them in the few books I could lay my hands on. Tubes with usable small signal amplification with a 12V supply could be made but delivering enough audio output power was impracticable. The solution was to step up the supply voltage with a vibrator or to use power transistors when they became available.

Quite some time ago, I collected several audio and RF tubes from a repair shop that had closed down in the 90s. I wanted to make some guitar amps and preamps for friends from the younger generation who'd come to highly value the tube sound. But I couldn't find a source for the sockets.

More recently, it's become possible to source almost anything from China, including tube sockets. My youngest son has turned out to be a gifted guitarist and I intended to build a tube amp while he's away in college, as a surprise gift for when he comes home for the holidays.

But alas, I can no longer find the tubes. I found a couple crushed on the floor of my old workshop. It must have happened when I hosted a two-week-long community event in my compound just before Christmas 2014 and things got shuffled around a lot. :-(

For the low level stages be sure to get some good sockets. The old black Bakelite type are very noisy. Fender used some decent sockets. Mica filled phenolic. Ceramic is probably better. Check out: